The present invention relates generally to an apparatus for training a waist portion of a human body, and more particularly relates to a physical instrument for exerting muscles to overcome a resistance to rotational motion of the waist portion of the human body.
A waist twisting motion is a kind of muscle training that is one of the basic physical exercises for a human body. A waist twisting motion carried out with the aid of the training apparatus has an effect on the expansion and constriction of oblique abdominal muscles and sterratus anteriors, latissimus dorsi, trapezius, fascia infraspinata, teres minor, and teres major, as well as the straight abdominal muscles of a human body. By this, the muscle strength can be increased and waist portion becomes thinner.
Such training apparata have commonly been proposed and put into practice. Japanese Utility Model Applications First PUblications (Jikkai) Sho 60-180461, sho 60-182072, sho 60-182073 and a Japanese Patent Application file No. sho 59-93589 disclose such structures of the training apparata.
These training apparata are formed like chairs in which a first portion on which a trainer sits and a second portion having handgrasps, are rotated through a predetermined angle in mutually opposite directions. In addition, pulleys are provided on the first and second portions, a belt extends between the pulleys so that the first and second portions can be caused to pivot in opposite directions thereby. Furthermore, a damper is provided to apply resistance to the pivotal movements of the first and second portions.
However, since the first and second portions are connected through the pulley and pulley belt, a transmission loss of the driving force between the first and second portions is generated by the belt and pulleys. In addition, since the damper uses, electrical power, power consumption accompanies use of the above-described training apparata and also production costs are increased because of the damper.